Apparatus for controlling the concentration of solutions which tend to foam



6; 1949 P A. KEENE 2,490,634

APPARATUS FOR COliTROLLING THE CONCENTRATION OF SOLUTIONS WHICH TEND T0FOAM Filed March 11, 1946 "1Cyl.

INVENTOR Paul/"141190120 BY Q 14/ ATTORNEY 4 Patented Dec. 6, 1949APPARATUS FOR CONTROLLING THE GON- CENTRATION F SOLUTIONS WHICH TEND TOFOAM Paul A. Keene, Syracuse, N. Y., assignor to Allied Chemical & DyeCorporation, a corporation of New York Application March ll, 1946,Serial No. 653,675

a Claims.

This invention relates to control apparatus for controlling theconcentration of solutions which tend to form foam or suds; for example,alkaline solutions containing organic detergents. In the specificationshereinafter, and claims, the term "foam" is used in a broad sense and isintended to include suds.

In dish washing machines, for example, it is common practice to spray adetergent solution from a body thereof on the dishes, after which thedishes are rinsed by spraying them with hot rinse water. The rinse waterusually collects in the body of wash solution where it causes somedilution, with consequent change in the concentratlon of this solution.A portion of the wash solution from the body thereof flows through anoverflow pipe during operation, thus maintaining the level of the bodyof solution substantially constant. As successive racks of dishes arewashed, the washing and rinsing cyces are repeated. During the course ofthe washing, detergent should be added to the wash solution to maintain,as nearly as practicable, a uniform concentration of detergent therein,i. e. to replace the detergent which is wasted in the overflow, and alsothat which reacts in each cycle to effect removal of dirt and otherconstitutents washed from the dishes. For best results, theconcentration of detergent in the wash solution should be maintainedwithin fairly narrow limits. Concentrations below the predeterminedlimit produce ineflicient washing and concentrations above this limitresult in unnecessarily large losses of detergent.

It has been proposed to control the concentration of such washingsolutions within relatively narrow limits by means of a controllerinvolving an electrode disposed in the solution and responsive tochanges in concentration, which electrode controls the feed of detergentsolution to the wash solution.

When such controllers are employed in washing machines employingdetergent solutions, such as are commonly used, which solutions in usetend to foam, certain difiiculties are encountered. For example, whenthe foam contacts the control electrode, due to the fact that the foamhas a very much higher resistance than the solution from which it arose,the electrode registers the resistance of the foam, and causes thecontroller to remain in the operating position, so that detergentcontinues to be fed even though the concentration of the solution isabove the desired predetermined value. This continuance of feed ofdetergent solution results in the production ill of, more foam and mayeventually lead to the solution overflowing the washer.

Among the objects of this invention is to protailed description thereof.

In the preferred embodiment illustrated on the drawing, the invention isshown incorporated in a dish washing machine and the present descriptionwill be confined to the present illustrated embodiment of the invention.It will be understood, however, that the novel features and improvementsare susceptible to other applications such, for example, as can washingmachines or other machines in which it is desired to maintain withinnarrow limits the concentration of a solution which tends to foam inuse. Hence, the scope of this invention is not confined to theembodiment herein described. The invention is broadly applicable to thecontrol of concentrations of any solute in-a solution the conductivityof which varies with the concentration of the solute; for example,aqueous solutions of electrolytes.

In the accompanying drawings,

Fig. 1 is a diagrammatic vertical sectional view partially in elevationillustrating a dish washing machine embodying this invention;

Fig. 2 is a wiring diagram showing a bridge type of electrical controlembodying this invention; and

Fig. 3 a fragmentary vertical section on an enlarged scale, as comparedwith Fig; 1, showing one form of detergent dispenser which may beassociated with the washing machine.

Referring to Fig. 1, the dish washing machine comprises a housing ill inwhich racks of dishes ii are placed on perforated supports [2. Top andbottom wash sprays I3, I! are arranged to be supplied with wash solutionunder pressure through branch pipes l5, I6 from a motor driven pump l'l,the suction intake I8 of which is in communication with a body ofdetergent solution l9 disposed in a tank 20 positioned near the-bottomof the washing machine. Hot rinse water is supplied from a pipe 2|having branches 22,

3 23 extending to the top and bottom rinse sprays 24, 25. It will beunderstood that the washer shown in the drawing represents onewell-known type of washer and the present invention may be applied notonly to this washer but to other s also.

I esirably the detergent solution may be a caustic soda, soda ash,modified soda or other alkaline solution, containing an organicdetergent such, for example, as that sold under the trade-mark Nacconol,(salts of alkyl benzene sulfonates, the alkyl group of which has anaverage carbon content of from 12 to 18 carbon atoms), or that soldunder the trade-mark Nytron," (organic nitrosation-sulfitation productsdisclosed in United States Patent No. 2,265,993 granted December 16,1941) or other solutions, the conductivities of which vary with theconcentrations of the solute, solutions with higher concen trationshaving higher conductivities.

In the operation of the dish washing machine, the dishes H are washed byoperating pump IT for a predetermined period of time, and then this pumpis stopped and the dishes are rinsed by supplying relatively hot rinsewater from the sprays 24, 25. Each rack of rinsed dishes, after rinsing,is removed and replaced by another rack of dishes to be washed, and thecycle of operation repeated. Rinse water from each cycle of operationdilutes the body of solution l9 and causes some of the latter to flowthrough the overflow pipe 26, the top of which is disposed at suchelevation within tank 20 as to maintain the solution therein at thedesired level. Thus the concentration of detergent in the body ofsolution i9 is progressively reduced by the reaction of the detergentwith food and other material on the dishes, by the dilution of thesolution with the rinse water,

and due to the overflow through pipe 26.

Detergent solution is supplied to the washing machine from a dispenser21 mounted on a bracket support 28 fastened to the side of the washer.The dispenser 21 is desirably in the form of a cylindrical container 29having a base 33, a discharge outlet 33 leading from the dispenser intoa discharge conduit 34, which in turn leads into the washer, adownwardly sloping plate 3| disposed just above the base 30 andextending completely across the container 29, and a concavo convexvertically extending member 32 having its ends welded or otherwisefastened to the inner walls of the container 29, and extending from nearthe top of container 29 to the plate 3 I. Thus, there is produced achannel 35, semi-circular in crosssection, extending vertically alongthe inner wall of container 29, and occupying a minor portion of thevolume thereof, and a compartment 36 occupying a major portion of thevolume of container 23, which compartment receives solid detergent to bedispensed. The concavo convex portion of member 32 defining a sidewallof compartment 36, as shown in Fig. 3, is perforated to place thecompartment 38 in. communication with channel 35; for. example, theintermediate portion of member 32 maybe a screen desirably-of 30-mesh. Aperforated distributor plate 31 is disposed across the top ofcompartment 36. A. cover 38 may be provided for the container 29 toprevent steam and vapor escaping when the cover reservoir 40 is alsoprovided with a valve opening or seat 42, flow through which iscontrolled by valve plug 43. Opening 42 communicates with a spout 44,the discharge outlet of which ls'disposed above distributor plate 31.Water, preferably hot water at a temperature of F., is supplied toreservoir 40 through water inlet line 45 which may be a branch line fromthe main rinse line 2|. Valve plug 43 is fastened to one end of valvestem 46, the other end of which is secured by a valve hinge pin 41 tothe armature 45'. Stem 45 passes through a flexible sleeve 43' which isfastened to the base wall of housing 38 and is secured to stem 46,thereby preventing moisture from entering the solenoid housing 33.

On activation, the solenoid armature 48' is raised, pulling the valveplug 43 from its seat against the action of a spring 49. Water alreadypresent in reservoir 40, along with fresh water from line 45, passesthrough opening 42 to the spout 44, and thence to distributor plate 31where it passes over or through the detergent in the compartment 35. Theresulting concentrated detergent solution flows through channel 35,discharge outlet 33 and conduit 34 into the washer, where it mixes withthe body of wash solution l3. As the quantity of water required todispense the required amount of detergent is small, of the order of 8 to10 gallons per hour, the dilution of the wash solution is by the minorportion of this water flowing through overflow pipe 4| and channel 35and not passing through the solid detergent-is negligible.

The controller, as shown in Fig. 2, involves a control circuit 50 and amain circuit 5|. The latter is energized from an alternating currentsource which is connected to the input terminals of the primary 52 of amulti-coil transformer 53. Disposed in the main circuit 5| is theoperating solenoid 48, a switch 54 which is normally open but which isadapted to be closed, as hereinafter described, by the control circuitto cause current to flow through the main circuit to energize solenoid48, and a signal lamp 55 shunted across the solenoid 48 and showing whencurrent is flowing in the main circuit, and the dispenser is, therefore,operative to dispense detergent solution to the washer.

The control circuit comprises variable resistors 56, 51 in a Wheatstonebridge arrangement, to one arm 58 of which are connected conductors 59,60, leading to a control electrode 5|. This electrode may be of anywell-known type for measuring conductivities of solutions, and desirablyconsists of a pair of closely spaced platlnized rods in a common casing.It is disposed in the washer within the body of solution i9 as shown inFig. 1. In parallel with the control electrode St is an auxiliaryelectrode 62. This electrode desirably may consist of two metallicplates 63, 54, say each approximately 2" long and 2 wide and closelyspaced, sa one-half inch apart, so that the electrode has a lowerresistance when foam fills the space between the plates than theresistance of electrode 6| when submerged in a solution of the desiredconcentration. The presence of foam between plates 63, 64 in effectshort circuits the control electrode 6|, i. e. materially decreases theresistance in the arm 58 of the Wheatstone bridge. As shown in Fig. l,electrode 62 is located at a point above the normal level of body ofsolution I!) where the foam will reach it quickly. Consequently, inoperation the dispensing of detergent solution will be stopped when foamreaches the electrode 62, which will edea take place before enoughdetergent is added to cause the solution to overflow the machine. Assoon as the foam dies down due, for example, to the presence of soil inthe wash water, the electrode 62 is left free and clear, becoming aninfinite resistance, and consequently exerting no further effect on thecontrol electrode ll.

Secondary coils 85, 88 of transformer 43 are connected by conductorswith points 48,." of the Wheatstone bridge. Secondary coil 88 suppliescurrent to the filaments 69, 10 of electronic tubes ll, I2. Tube 1|desirably is a conventional triode or pliotron, and tube I2 desirably isof a type to produce a higher emission of electrons, such into thewasher where is collects in tank 20.

As the concentration of the solution in tank 20 increases, theresistance across the electrode as the well-known thyratron. Tube II, ascon ventlonal, comprises a cathode 12, a grid I3 and an anode 14. Thetube 12 comprises a cathode II, a grid 16, a screen electrode I1 and ananode I8.

Secondary coil 19 of the transformer 53 is in circuit with points 80, 8|of the Wheatstone bridge. Located in this circuit is the grid circuit ofthe tube H as shown in Fig. 2. The output anode circuit of the tube Iiincludes a resistor 14 across which the input circuit of the tube 12 isshunted. In the output anode circuit of tube 12 is disposed relay 82 foroperating switch 54 in the main circuit 5|. Resistor I4 is such thatwhen the current flowing through the output anode circuit of tube Hreaches a certain value, the potential drop across the resistor 14'causes the tube I2 to pass sufllcient current through its anode circuitto operate the relay 82, to close switch 54.

The control circuit hereinabove described, except for the electrodes GI,62 and the lead wires connected thereto, and the parts of the maincircuit except for the solenoid 48 and signal lamp 45, are allpreferably disposed in a control box 83 which may be positioned onsupport 28 next to dispenser 21. The control is, therefore, readilyapplicable to existing washers not equipped with controls, particularlyin cases where it is desired to supply such washers with dispense rs ofthe type hereindescribed. When modifying a washer to embody thisinvention, it is only necessary to install the dispenser and control boxon the side of the washer, connect the discharge of the dispenser withthe washer, and place the electrodes GI, 64 within the washer in therelative 50 positions shown.

In operation, resistance 51 is set at a point previously determined bycalibration, which point is dependent upon the desired concentration of8! decreases, and a gradual decrease in the instantaneous voltagesbetween the grid I3 and cathode 12' of tube ll occurs, which causes anincrease in the current flowing through resistor 14'. The resultantincrease in voltage appearing across the control grid 18 and cathode I5of tube 12 finally reaches a point where the control grid 16resumescontrol and extinguishes the tube, stopping the current flowthrough the relay 82, deenergizing it, and opening the switch 54,whereupon, under the influence of spring 49, valve stem 48 returns valveplug 43 to its seat 42. Water thereafter supplied through line 45 flowsfrom reservoir 40 through overflow pipe 4| into and through passage 35and not to the body of detergent maintained in compartment 36 of thedispenser 21.

When foam is produced,'as is frequently the case when employing asolution containing an organic detergent, and the foam rises to a pointsuch that it enters between'the plates 63, 64 of the auxiliary electrode62, the resistance in the arm 58 of the Wheatstone bridge is therebyreduced so that, as hereinabove described, valve plug 43 is seated inseat 42 and the water flows through channel 35 and not through the bodyof detergent. Hence, as long as foam is present at a level such that itcontacts the auxiliary elec-' trode 62, no detergent is fed to thewasher. When the foam dies down, the auxiliary electrode 62 is left freeand clear, exerting no further effect on the control electrode 8| andpermitting this electrode to maintain the concentration of the deter-18121125111 the washer within the desired narrow Since certain changesmay be made in the above construction and different embodiments of theinvention could be made without departing from the scope thereof, it isintended that all matter contained in the above description or shown inthe accompanying drawing shall be inthe detergent used. Resistance 56 islikewise set reted at a point previously determined by calibration, p asillustrative and not In a limiting which point is dependent upon thetemperature of the body of wash solution it. Since the grid I3 and plate14 of tube Ii are approximately 180 out of phase, an increase in theresistance of the solution, due to a decrease in concentration, causes agradual increase in the instantaneous voltages between the grid 18 andcathode i2 00 which tends to foam, which which in turn causes a decreasein the current flow through the resistor 74'. The control voltagedeveloped across resistor M', applied across the control grid 16 andcathode of tube 12, is sufllcient to prevent tube 12 from firing beforethe concentration of the solution starts to decrease. When the decreasein voltage drop across resistor 14', resulting from the increase inresistance across the electrode 5!, reaches a critical value, dependingupon the tube employed, the control grid 16 loses control andthe tube 12fires which causes current to flow through the 76 sense.

What is claimed is:

l. A control for maintaining within narrow limits the concentration of abody of solution comprises in combination, a control electroderesponsive to changes in concentration in said body of solution, acontrol circuit in which said electrode is disposed, said controlcircuit effecting feed of material to said body of solution responsiveto changes in concentration to maintain said concentration within saidnarrow limits and an auxiliary electrode in said control circuit anddisposed above the normal level of said body of solution, said auxiliaryelectrode being adapted to be contacted by foam rising above the normallevel of said body of solution, and while thus contacted rendering thecontrol circuit inoperative and preventing the feed of further materialto said body of solution.

2. A control for maintaining within narrow limits the concentration of abody of solution which tends to foam, which comprises in com-.

bination, a control electrode responsive to changes in concentration insaid body of solution, a control circuit in which said electrode isdisposed, said control circuit efiecting feed of material to saidsolution responsive to changes in concentration to maintain saidconcentration within said narrow limits, and an auxiliary electrodedisposed above the normal level of said body of solution and arranged tobe contacted by foam produced in said body of solution, said auxiliaryelectrode being connected in parallel with the control electrode andwhen contacted by said foam rendering the control electrode inoperative.

3. A control for maintaining within narrow limits the concentration of abody of alkaline solution which tends to foam, which comprises incombination, a dispenser for feeding alkaline solution to said body ofsolution, a control electrode disposed in said body of solution, meansoperated by said electrode for causing said dispenser to feed alkalinesolution to said body of solution when the concentration thereof fallsbelow a predetermined value, means for interrupting the feed of saidalkaline solution to said body of solution when the concentrationthereof is restored to said predetermined value, an auxiliary electrodedisposed above the normal level of said body of solution and arranged tobe contacted by foam produced in said body of solution, said auxiliaryelectrode being connected in parallel with the control electrode, andwhen contacted by said foam functioning to short circuit said controlelectrode to render it inoperative and prevent feed of further solutionto said body of solution.

4. A control for maintaining within narrow limits the concentration of abody of solution which tends to foam, which comprises in combination, aWheatstone bridge, a control electrode responsive to changes inconcentration of said solution connected to one arm of said bridge, anauxiliary electrode connected in parallel in the circuit containing saidcontrol electrode, said auxiliary electrode being arranged above thenormal level of said body of solution and, when contacted by foam,decreasing the resistance in said arm of said Wheatstone bridge, acontrol circuit in which said bridge is located, a relay operated bysaid control circuit, a main circuit, a switch in said main circuitoperated by said relay, and means operated by said main circuit fordispensing detergent to said body of solution to maintain theconcentration thereof within said narrow limits.

5. A control for controlling the concentration of a body of detergentsolution which tends to foam, in combination, a dispenser for dispensingdetergent solution to said body of solution, a control electrodedisposed within said body of solution, an auxiliary electrode disposedabove the normal level of said body of solution, a Wheatstone bridge,said control electrode and said auxiliary electrode being connected inparallel in a circuit connected with one arm of said bridge, a controlcircuit in which said Wheatstone bridge is disposed, a relay operated bysaid control circuit, a main circuit, a switch in said main circuitoperated by said relay and a solenoid in said-main circuit for efiectingoperation of said dispenser responsive to changes in concentration ofsaid body of solution as indicated by said control electrode.

PAUL A. KEENE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,231,211 Halsey et a1. Feb. 11,1941 2,370,609 Wilson et al Feb. 27, 1945

